In Vitro Evaluation of Ferrihydrite as an Enterosorbent for Arsenic from Contaminated Drinking Water

Abstract

Arsenic (As) is a toxic trace element found in groundwater due to natural and industrial processes. Exposure has been linked to cancers of the bladder, lungs, skin, kidneys, nasal passages, liver, and the prostate. Arsenic in drinking water is a problem in many countries, notably Bangladesh and Taiwan. The purpose of this research was to utilize binding isotherms, a simulated gastrointestinal (GI) model, and the adult Hydra bioassay to evaluate ferrihydrite's potential to bind As and serve as a potential enterosorbent for As found in drinking water. A variety of clay minerals and synthesized iron oxides including ferrihydrite were screened for their ability to bind As(III), as sodium arsenite, and As(V), as sodium arsenate. After ferrihydrite was demonstrated to be the most effective sorbent for both As species, adsorption isotherms were performed. All isotherm data were fit to the Langmuir equation to determine adsorption capacity (Q max ). Ferrihydrite bound 96% of As(III) and 97% of As (V) in the screening studies and had a Q max of 1.288 mol/kg for As(III) and 0.744 mol/kg for As(V). Using a simulated GI model, ferrihydrite was found to effectively adsorb As(V) and As(III) in the stomach and intestine. Ferrihydrite (0.25% w/w) protected adult hydra at levels up to 200 times the minimal effective concentration (MEC) for As(III) and up to 2.5 times the MEC for As(V). These experiments confirm that ferrihydrite is a high capacity sorbent of As, and that it is effective at removing As in a simulated GI model. These results suggest that ferrihydrite could be used as a potential enterosorbent for As found in drinking water. Future work will focus on verifying ferrihydrite's safety and efficacy in vivo.

Size- and Composition-Dependent Toxicity of Synthetic and Soil-Derived Fe Oxide Colloids for the NematodeCaenorhabditis elegans

“…Dispersed iron oxides (FeOx), i.e., FeOx colloids, are highly reactive Fe-NM that exceed the already distinct reactivity of noncolloidal FeOx. , In addition to nitrate, Mn­(IV) oxides and sulfate, FeOx colloids may also serve as highly available electron acceptors for microbial anaerobic biodegradation of hydrocarbon groundwater contaminants. Furthermore, FeOx colloids are synthesized and applied in cleaning-up sediments and drinking water by binding toxic metals, , in wastewater treatment, and for biomedical purposes . Consequently, synthetic FeOx colloids will be increasingly released into the environment, posing a potential risk for the biota of groundwater and surface water ecosystems.…”

Response of bacteria and meiofauna to iron oxide colloids in sediments of freshwater microcosms

“…One pilot field study showed that, in spite of high FeOx concentrations in the injection solution (∼10 g L –1 ), relatively low concentrations were measured downstream of the injection well (10–20 mg L −1 of groundwater; ). Given the wide‐ranging possible use of FeOx colloids in detoxification of sediment and drinking water by binding toxic metals , in wastewater treatment , and for biomedical purposes , input of FeOx colloids in surface water (including sediments) is likely. Therefore, it is important to determine the ecotoxicological risks of FeOx colloids associated with their release into the environment, as has been done for nanoscale zerovalent irons .…”

Molecular characterization of a catalase from Hydra vulgaris

“…Our laboratory (Mayura et al, 1991; Lum et al, 2003; Taylor et al, 2009) and other have used the changes in external gross morphology and anatomy, and physiology are useful as markers of toxicity or toxicity end points in the hydra bioassays (Johnson et al, 1982; Pollino and Holdway, 1999; Karntanut and Pascoe, 2000; Holdway et al, 2001; Pascoe et al, 2002; van Dam et al, 2010; Vernouillet et al, 2010; Ferreira et al, 2011; Trenfield et al, 2011). At molecular level, it may be postulated that, the detection of stress and/or redox sensitive messages in hydra can constitute an early-warning marker for the presence of potentially deleterious agents in water.…”